bought a small xmas tree jan 2011 and have repotted it twice===last couple of weeks, the needles have all turned a brown colour but there do seem to be new green shoots---could this be the cold winds recently or is it on its way out??

In a pot, too, any mistakes in watering will be magnified, since most conifers in containers have no forgiveness for drought. Since it has green tips, though, you are at least provisionally forgiven! : )
Do you know what species it is, 80smaniac? Judicious feeding might help it to recover faster, but some species have idiosyncracies in their food preferances.